A combined study of polarization effects in PVDF

NMR and IR provide only information about the extent of the polarization which is averaged over the sample thickness. LIMM (laser intensity modulation method) has been used to investigate the polarization (electric dipole) profile over the thickness in a PVDF film. It can be shown that the polarization profile has a maximum in the middle of the film (depending on the poling conditions) and vanishes in the proximity of the electrodes (about 20% of the material). The NMR investigation adds the information that the relevant polarization part in the inner region of the film is due to effects in the crystallites only. The combination of different methods in order to discuss polarization methods reveals a fairly complex picture regarding the interplay of crystallinity, crystalline modifications, crystallite size, dipole orientation and and their distribution over the sample thickness. The increase of the β-content and orientational effects are concentrated in the middle range over the thickness. That means, the changes in the relevant range are, spatially resolved, much larger as deduced from spectroscopic data alone. Vice versa, NMR spectroscopy adds the information that changes occur more or less exclusively in the crystalline phase